In order to create various light effects and mood lighting in connection with concerts, live shows, TV shows, sport events or as a part of an architectural installation light fixtures creating various effects are getting more and more used in the entertainment industry. Typically, entertainment light fixtures create a light beam having a beam width and a divergence and can for instance be wash/flood fixtures creating a relatively wide light beam with a uniform light distribution or it can be profile fixtures adapted to project images onto a target surface.
Light emitting diodes (LED) are due to their relatively high efficiency, low energy consumption, long lifetime, and/or capability of electronic dimming, becoming more and more used in connection with lighting applications. LEDs are used in lighting applications for general illumination such as wash/flood lights illuminating a wide area or for generating wide light beams e.g. for the entertainment industry and/or architectural installations. For instance like in products like MAC 101™, MAC 301™, MAC 401™, MAC Aura™, MAC Quantum™, Stagebar2™, Easypix™, Extube™, Tripix™, Exterior 400™ series provided by Martin Professional. Further LEDs are also being integrated into projecting systems where an image is created and projected towards a target surface. For instance like in the product MAC 350 Entrour™ provided by Martin Professional.
Different kinds of LEDs are currently commercially available. For instance LEDs may be provided as colored LEDs emitting light having a relatively narrow spectral bandwidth and thus emitting light of a single color. Typically, LED based lighting products include a number of these LEDs of different colors, and light generated by the LEDs provided are combined into an outgoing light beam. The intensity of each color can be adjusted relatively to each other whereby the color of the outgoing light beam can be varied as known in the art of additive color mixing. These lighting products can thus create any color within the color gamut defined by the color of the LEDs. Typically, this kind of lighting products include red LEDs, green LEDs and blue LEDs and are known as RGB lighting products. The RGB lighting products can produce red, green and blue by turning the LED of only one color on while turning the remaining colors off. Further, the RGB products can produce white light by turning all colors on (and approximately at the same intensity) at the same time. However, the color rendering index (CRI) of the white light is very low due the fact that the white light is created by combining light with a narrow spectral bandwidth. The consequence is that an object illuminated by this white light, is not reproduced in its natural colors (as it appears when illuminated by sun light).
LEDs are also provided as white LEDs that are adapted to emit light having a broad spectral bandwidth and these may further be provided with different color temperature. These LEDs have a high CRI, as they emitted light over a large spectral bandwidth and are thus used in LED based lighting products to create bright white light, which can be used to illuminate objects and reproduce the objects in substantially its natural color. However, LED based lighting product based on white LEDs cannot create colored light beams without using a color filter as known in the art of subtractive color filtering.
RGBW LED based lighting products, where a number of single color LEDs and a number of white LEDs are combined, are also provided in order to be able to create different colors using additive color mixing and to improve the CRI and the efficacy of the white light. This is achieved by replacing a number of the colored LED with a number of the white LEDs. The white LEDs provide light having a broad spectral bandwidth and the CRI of the white light produced by such device is thus improved by white LEDs and the intensity of the white light is also increased. However the down side is that the intensity of the satiated colors are reduced since there are fewer of these.
The LEDs are also provided in packages having a multiple amount of LED dies emitting light of different color and additionally also a LED die emitting white light. The LED dies can be controlled individual, whereby the relative intensity of the light emitted by each dies may be varied in relation to each other whereby the color of the outgoing light can be varied as known in the art of additive color mixing. Typically, these LED packages includes a red die, green die, blue die and a white die and are known as RGBW 4in1 LEDs. The RGBW 4in1 LED are often used in RGBW LED based lighting products as described above.
In general, it is desired to have a multi-colored LED lighting product with a high lumen and also a high CRI. However, this is hard to achieve with the LED types described above due to Etendue limitations as it is not possible to combine light from an unlimited amount of light sources into a light beam. The known LED based lighting products are as a consequence often designed for specific purposes and it is often necessary to have a large range of LED based lighting products in order to be able to provide a large variety of lighting solutions. This is especially the case in connection with projecting systems, where the light is coupled through an optical gate, where an image creating objects (GOBO) is positioned. An optical projecting system collects the light from the optical gate and is adapted to image the optical gate (and thus also the image creating object) at a target surface. The light beam is very narrow when it passes the optical gate and such projecting systems are thus limited by Etendue. The Etendue, E=A*Ω, at the gate through which light is emitted has a limited opening area A and the imaging optics only collect light from a limited solid angle Ω. For light sources, the Etendue can be calculated in the same way, where A is the radiating area, and Ω is the solid angle it radiates into. Further, it is also desired to have very compact illumination devices, which is difficult to achieve when more light sources are being integrated into the same illumination device.
In projecting systems, the light is generally collected into an optical gate where the image is generated, and an imaging optical system projects the gate onto a target surface. International Publication No. WO0198706, U.S. Pat. No. 6,227,669 and U.S. Pat. No. 6,402,347 disclose lighting systems comprising a number of LEDs arranged in a plane array where a converging lens is positioned in front of the LED in order to focus the light, for instance to illuminate a predetermined area/gate or for coupling the light from the diodes into an optical fiber.
U.S. Pat. No. 5,309,277, U.S. Pat. No. 6,227,669, International Publication No. WO0198706, Japanese Publication No. JP2006269182 A2, European Publication No. EP1710493 A2, U.S. Pat. No. 6,443,594 disclose lighting systems where the light from a number of LEDs is directed towards a common focal point or focusing area, for instance by tilting the LEDs in relation to the optical axis (Japanese Publication No. JP2006269182 A2, International Publication No. WO0198706, U.S. Pat. No. 5,309,277) or by using individually refracting means positioned in front of each LED (U.S. Pat. No. 6,443,594, U.S. Pat. No. 7,226,185B, European Publication No. EP1710493).
International Publication No. WO06023180 discloses a projecting system comprising a LED array with a multiple number of LEDs where the light from the LEDs is directed towards a target area. The LEDs may be mounted to a surface of a curved base.
The prior art fixtures try to increase the lumen output by adding as many light sources as possible. The consequence is, however, that the efficiency with regard to power consumption versus light output is very low, as it is fundamentally only possible to effectively utilize light sources of same or less Etendue as the imaging optics in this kind of optical system. So if the source Etendue is a close match to the Etendue of the imaging system there are no gains in using multiple sources in order to increase the light output (intensity/lumen) as the Etendue of the light sources then will be larger than the Etendue of the imaging system and the imaging system is thus not capable of collecting the light.
International Publication Nos. WO11076213 and WO11076219 disclose an illumination device comprises a light source module generation light, an aperture delimiting the optical gate and a projecting system adapted to image the optical gate at a target surface. The light source module comprises a number of light sources and a number of light collecting means. The light collecting means comprise a central lens aligned along and a peripheral lens at least partially surrounding the central lens. The central lens collects and converts a first part of the light from the light source images the light source between the aperture the projecting system. The peripheral lens part collects and converts a second part of said light from said light source and is adapted to concentrate said second part of said light at said aperture. The light source module comprises a cooling module including a number of interconnected plane mounting surfaces angled in relation to each other and where the light sources is arranged on said plane mounting surfaces. The cooling module comprises a first side including the mounting surfaces and a second side including a number of cooling fins defining a number of radial air channels.
Even though the illumination device disclosed by International Publication Nos. WO11076213 and WO11076219 is very effective, it has some disadvantages as it is relatively expensive to manufacture as the LEDs and TIR lenses needs to be arranged individually.